[R] Syntax for geom_point in ggplot2, distinguishing point types.

[Jeff Newmiller]

My general approach is to import data without letting the import convert to factors. Then I explicitly create my factors with the levels I want them to have, with explicit vectors specified for the levels. Fixing this after the analysis is possible but a headache.

On March 28, 2020 5:46:25 PM PDT, Rolf Turner <r.turner using auckland.ac.nz> wrote:
>
>I have an application in which I want to plot points with different 
>colours and symbols to distinguish (three) types of point.  I thought I
>
>had it figured out, mostly by a trial-and-error approach and by 
>simple-mindedly following instructions from others, without (sad to
>say) 
>really understanding what I was doing.
>
>I have now encountered an example where my syntax screws up, and I
>can't 
>see how to fix it in a coherent and generally applicable way.  The 
>problem arises if the data column (factor) specifying the point types
>is 
>missing one level.  When this happens, the types get out of synch.
>
>I have attached a source-able file "demo.txt" and the two data sets
>upon 
>which it depends as "data1.txt" and "data2.txt" (dput() format).
>
>The result from using the data from "data1.txt" (plotObj1) demonstrates
>
>the problem, i.e. the unwanted phenomenon.  The result from using the 
>data from "data2.txt" (plotObj2) is "as it should be".
>
>In the data from data1.txt the "extremes" column, which specifies the 
>point type, is missing the level "0":
>
>>        table(Dat1$extremes)
>> 
>>        0 intermed        1 
>>        0       39       43 
>
>As you will be able to see, the plot of these data has the "0" symbol
>(a 
>triangle) where there should be an "intermed" symbol (a solid dot), and
>
>the "intermed" symbol where there should be a "1" symbol (an
>upside-down 
>triangle).
>
>The data from data2.txt have an extremes column with all three levels 
>and the corresponding plot is as desired.
>
>I'm pretty sure that the solution to my problem is quite simple, but I 
>am too stupid to figure it out.  Can anyone guide me in the right
>direction?
>
>Thanks.
>
>cheers,
>
>Rolf Turner

-- 
Sent from my phone. Please excuse my brevity.